Started textnodes, renamed tool with wrong name, started field configuration system

source/data/field-configuration.mjs

@@ -0,0 +1,24 @@
+import { Invalid_Data } from '@efforting.tech/errors';
+
+export class Field_Configuration {
+	constructor(name, validator=null, expected=undefined) {
+		Object.assign(this, { name, validator, expected });
+	}
+
+	check_validation(value) {
+		const { validator } = this;
+
+		return !validator || validator(value);
+	}
+
+	validate(value, target=undefined) {
+		const { validator, name, expected } = this;
+		if (!this.check_validation(value)) {
+			throw new Invalid_Data({
+				name, validator, value,
+				target, expected,
+			});
+		}
+	}
+
+}

source/errors.mjs

@@ -1,5 +1,18 @@
 import { inspect } from 'node:util';
 
+// § GROUP: Configuration field errors
+
+export class Invalid_Data extends Error {
+	constructor(data) {
+		const { value, target, expected, validator, name } = data;
+		const type = value === null ? 'null' : typeof value;
+		const target_info = target ? inspect(target) : 'unknown target';
+		const expected_desc = expected ?? `data that would pass validation using ${validator}`;
+		super(`Data validation failed for field "${name}" of ${target_info}. Encountered data of type "${type}" while expecting "${expected_desc}".`);
+		this.data = data;
+	}
+}
+
 // § GROUP: Resolving errors
 
 export class Item_Unresolvable extends Error {